Defined, serum-free media will be developed for rodent and human epithelial cells. The requirement for serum protein will be reduced or eliminated by substituting known growth factors and by altering the basic nutrients as necessary. Macromolecular factors still required will be isolated and characterized. Other culture parameters such as cell dissociation methods and the culture dish surface will also be optimized. Cultures will be characterized by morphological, ultrastructural chromosomal and growth criteria. Two human epithelial cells, NP-2s from neonatal prostate and NB 128 from adult bladder, as well as epithelial cells from primary syrian hamsters bronchus cultures and mouse keratinocytes will be used. The efficacy of nutrient medium MCDB 402 in the mouse 3T3 transformation assay will also be assessed. The goal is not only to obtain appropriate growth control of target cells for transformation studies but to provide a baseline for comparison of the growth respone to normal and trasformed cells.